Bubble balancers are widely used in automotive repair shops and garages and basically include a base supported on casters for movement of the unit from one place to another and having an upright rigid post to the top of which a wheel support is pivoted mounted on a universal type pivot such, for example, as a ball and platen. A 360.degree. spirit level is mounted on the wheel support to indicate when the wheel and thus the wheel support lies in a horizontal plane. In use, a wheel to be balanced is placed on the wheel support and the bubble in the spirit level is observed to indicate the direction in which the wheel is inclined from the horizontal plane. Weights are then added at the appropriate places along the rim of the wheel until the wheel lies in a perfectly horizontal plane as indicated by the fact that the bubble in the level is centrally disposed therein. In order to speed up this operation it is the usual practice to incorporate some form of damping means in the balancer and a common type is an open liquid reservoir mounted to the base and containing a viscous liquid such as, for example, oil. A baffle depends from the pivotally mounted wheel support into the viscous liquid thereby causing the rotor and the support on which it is mounted to quickly reach the equilibrium rest position.
Bubble balancers of this type are subjected to rough handling and in order to prevent damage to the sensitive pivot assembly various means have been employed including a lever operated linkage for holding the wheel support off the pivot assembly except when a wheel is to be balanced. Another means for protecting the sensitive pivot assembly is to incorporate resilient means in the pivot assembly to absorb any sudden shocks which might otherwise be transmitted to the pivot assembly when a heavy wheel is dropped on the balancer. This latter means has proven to be extremely successful, but since the wheel support is always mounted by the pivot assembly it is free to rock back and forth when the wheel balancer is moved from place to place. This can cause the oil in the damping reservoir to splash out on the floor. Various types of baffles have been employed to prevent this from occurring but they have not been entirely satisfactory. Nevertheless, there are advantages to a wheel balancer system in which the wheel support is at all times supported by the pivot assembly.